Listeriolysin O: This major virulence factor generates pores in phagosome membranes, which allows phagocytosed L monocytogenes to escape into the cytoplasm of monocytes and avoid lysosomal destruction.
Actin-based transcellular spread: The organism hijacks the actin-based cellular motility mechanism of host cells, which allows it to spread to adjacent cells without reentering the extracellular space. This significantly reduces exposure of L monocytogenes to antibodies and phagocytic cells.
Because of these adaptations, antibody- and phagocyte-mediated destruction of the pathogen is impaired; therefore, infections are controlled primarily by the cytotoxic T-cell response.
